1. Field of the Invention
A continuously variable transmission apparatus according to the present invention is utilized as an automatic transmission for use with an automobile.
2. Description of the Related Art
A toroidal-type continuously variable transmission apparatus has already been known as a kind of transmission constituting a transmission for use with an automobile. Such a toroidal-type continuously variable transmission apparatus that has already been put into practice in some applications in the aforementioned manner is of so-called double cavity type, wherein power is transmitted from an input section to an output section by way of two separate systems provided in parallel with each other. Toroidal-type continuously variable transmission apparatus described in U.S. Pat. No. 5,033,322 and U.S. Pat. No. 5,569,112 and those described in numerous other publications have already been known as examples of such a toroidal-type continuously variable transmission apparatus. A basic structure of the toroidal-type continuously variable transmission apparatus will be described by reference to FIG. 8.
The toroidal-type continuously variable transmission apparatus shown in FIG. 8 has an input shaft 1. Input side disks 2, 2 are provided at respective areas close to a base end section (i.e., a left-side portion in FIG. 8) and an extremity section (i.e., a right-side portion in FIG. 8) of the intermediate section of the input shaft 1. The input side disks 2, 2 support ball splines 4, 4 such that input side surfaces 3, 3 consisting of toroidal surfaces are mutually opposed with respect to the input shaft 1. Therefore, the input side disks 2, 2 are supported so as to rotate in synchronism with the input shaft 1 such that the input side disks 2, 2 can be displaced in the axial direction of the input shaft 1.
A rolling bearing 5 and a pressing apparatus 6 of loading cam type are interposed between a base end section (the left end section shown in FIG. 8) of the input shaft 1 and an exterior surface of the input side disk 2. A cam plate 7 constituting the pressing apparatus 6 is set so that the cam plate can be rotatably driven by a drive shaft 8. On the other hand, a loading nut 9 and a flat leaf spring 10 having great resiliency are interposed between the extremity (the right end shown in FIG. 8) of the input shaft 1 and an outer side surface of the other input side disk 2.
An intermediate section of the input shaft 1 penetrates through a through hole 13 formed in a partition section 12 provided within a casing 11 housing the toroidal-type continuously variable transmission apparatus (see FIG. 1 showing an embodiment of the present invention). A cylindrical output cylinder 14 is rotatably supported by a pair of rolling bearings 15, 15 on an internal diameter side of the through hole 13. An output gear 16 is fixedly fitted around an outer periphery of the intermediate section of the output cylinder 14. A pair of output side disks 17, 17 are provided on the respective ends of the output cylinder 14 which protrude from outside surfaces of the partition section 12 and are supported so as to rotate in synchronism with the output cylinder 14 by means of spline engagement. In addition, a structure for rotatably coupling the pair of output side disks to both ends of the output cylinder and a structure for coupling inside-diameter portions of the outside surfaces of the output side disks to end sections of a sleeve by means of irregularity engagement, as described in U.S. Pat. No. 6,375,595, which is an another case being different from the above described means of spline engagement, have already been known as structures for rotatably coupling the pair of output side disks to the respective end sections of the output cylinder.
In this state, output side surfaces 18, 18 of the output side disks 17, 17, the side surfaces consisting of toroidal surfaces, oppose the input side surfaces 3, 3. Alternatively, needle roller bearings 19, 19 are interposed between some portions of inner peripheral surfaces of the output side disks 17, 17 protruding from the edge of the output cylinder 14 and an outer peripheral surface of the intermediate section of the input shaft 1. And, rotation and axial fluctuations of the output side disks 17, 17 with respect to the input shaft 1 are made variable while the load exerted on the output side disks 17, 17 is supported.
And, a plurality of power rollers 20, 20 (in general, two or three) are provided in a space (cavity) defined between the input and output side surfaces 3 and 18 around the input shaft 1. Each of the power rollers 20, 20 has a circumferential surface 21 which is brought into contact with the input and output side surfaces 3, 18 and formed into a spherical protruding surface. The power roller 20 is supported on an inner side of a trunnion 22 by means of a support shaft 23 and a plurality of roller bearings so as to be rotatable and slightly swingable.
Further, the trunnion 22 supports an axle provided on both ends thereof (i.e., with respect to a direction from the front side to the rear side of FIG. 8) on a support plate 24 (see FIGS. 1 through 3 showing an embodiment of the present invention) provided within the casing 11 such that the axle is swingable and displaceable in the axial direction. The trunnion 22 supports the axle such that the axle becomes freely movable in a counterclockwise direction and a clockwise direction in FIG. 8 and is displaced in the axial direction of the axle (i.e., the vertical direction in FIG. 1 and the direction from the front side to the rear side of FIG. 8) by means of an unillustrated actuator.
When the toroidal-type continuously variable transmission apparatus having the foregoing construction is driven, the input side disk 2 is rotatably driven by way of the pressing apparatus 6 by means of the drive shaft 8. The pressing apparatus 6 rotatably drives the input side disk 2 while generating axial thrust. The pair of input side disks 2, 2 including that input side disk 2 are rotated synchronously while being pressed against the respective output side disks 17, 17. Consequently, rotation of the input side disks 2, 2 is transmitted to the respective output side disks 17, 17 by way of the respective power rollers 20, 20. The output gear 16 coupled to the respective output side disks 17, 17 is rotated by way of the output cylinder 14.
When a transmission ratio between the drive shaft 8 and the output gear 16 is changed, the trunnions 22, 22 are displaced in the direction from the front side to the rear side of FIG. 8 by means of an unillustrated actuator. In this case, the trunnions 22, 22 of an upper half section in FIG. 8 and the trunnions 22, 22 in a lower half section in FIG. 8 are displaced in opposite directions to the same extent. An aspect of the force applied, in a tangential direction, to a contact section between the circumferential surfaces 21, 21 of the power roller 20 and the input and output side surfaces 3, 18 is changed in association with such a displacement. By means of the force in the tangential direction, the trunnions 22, 22 are swung around the axles provided on the respective end sections thereof.
In association with the swinging action, the positions of the contact sections between the circumferential surfaces 21, 21 of the power roller 20 and the input and output side surfaces 3, 18 are changed with respect to the radial directions of the side surfaces 3, 18. As the contact sections change toward the outside with respect to the radial direction of the input side surface 3 and the inside with respect to the radial direction of the output side surface 18, the transmission ratio is changed to acceleration. On the other hand, as the contact section changes toward the inside with respect to the radial direction of the input side surface 3 and the outside with respect to the radial direction of the output side surface 18, the transmission ratio is changed to deceleration.
For the case where the toroidal-type continuously variable transmission apparatus that is constructed and operates in the aforementioned manner is built in an actual automobile, construction of a continuously variable transmission apparatus by combination of the variable-speed drive with a differential unit of gear type, such as a planetary gear mechanism, has already been proposed. FIG. 9 shows a continuously variable transmission apparatus described in U.S. Pat. No. 6,251,039 from among the continuously variable transmission apparatus which have already been proposed. This continuously variable transmission apparatus is of a so-called geared neutral type, wherein rotation of an output shaft can be switched between forward rotation and rearward rotation with a stop therebetween while the input shaft is being rotated in one direction. The continuously variable transmission apparatus is constructed by combination of a toroidal-type continuously variable transmission 25 with a planetary gear mechanism 26. Of these transmissions, the toroidal-type continuously variable transmission 25 comprises the input shaft 1; the pair of input side disks 2, 2; an output side disk 17a; and the plurality of power rollers 20, 20. In the illustrated example, the output side disk 17a has a structure in which a pair of output side disks are integrated together by means of abutting the outer surfaces of the disks against each other.
The planetary gear mechanism 26 comprises the input shaft 1, and a carrier 27 fixedly coupled to one input side disk 2 (i.e., the right input side disk shown in FIG. 9). A first transmission shaft 29 having planetary gears 28a, 28b secured on respective ends of the shaft is rotatably supported by an intermediate portion of the carrier 27 in the radial direction thereof. A second transmission shaft 31 having sun gears 30a, 30b secured on respective ends thereof is rotatably supported in a manner concentric with the input shaft 1 on the side opposite the input shaft 1 with the carrier 27 sandwiched therebetween. The planetary gears 28a, 28b are engaged with a sun gear 33 fixed to the extremity (i.e., the right end section in FIG. 9) of a hollow rotary shaft 32 whose base end section (i.e., the left end section in FIG. 9) is coupled to the output side disk 17a, or with the sun gear 30a fixed to one end section (i.e. the left end section in FIG. 9) of the second transmission shaft 31. One of the planetary gears 28a (i.e., the left planetary gear 28a shown in FIG. 9) is engaged with a ring gear 35 rotatably provided around the carrier 27 by way of the other planetary gear 34.
On the other hand, Planetary gears 37a, 37b are rotatably supported on a second carrier 36 provided around the sun gear 30b fixed to the other end section (i.e., the right end section in FIG. 9) of the second transmission shaft 31. The second carrier 36 is fixed to the base end section (i.e., the left end section in FIG. 9) of the output shaft 38 disposed concentrically with the input shaft 1 and the second transmission shaft 31. The planetary gears 37a, 37b engage with each other, and the planetary gear 37a is engaged with the sun gear 30b, and the other planetary gear 37b is engaged with a second ring gear 39 rotatably provided around the second carrier 36. The ring gear 35 and the second carrier 36 are removably engaged with a low-speed clutch 40, and the second ring gear 39 and a stationary portion of a housing are removably engaged with a high-speed clutch 41.
In the case of the continuously variable transmission apparatus shown in FIG. 9 such as that described previously, the power of the input shaft 1 is transmitted to the output shaft 38 by way of the ring gear 35 in a so-called low-speed mode in which the low speed clutch 40 is connected and the high-speed clutch 41 is disconnected. The transmission ratio of the entire continuously variable transmission apparatus; that is, a transmission ratio of the input shaft 1 to the output shaft 38, is changed by means of changing the transmission ratio of the toroidal-type continuously variable transmission 25. In such a low-speed mode, the transmission ratio of the entire continuously variable transmission apparatus is changed infinitely. Specifically, the rotation of the output shaft 38 can be switched between forward and rearward with a stop therebetween while the input shaft 1 is rotated in one direction, by means of adjusting the transmission ratio of the toroidal-type continuously variable transmission 25.
During acceleration or constant-speed traveling of the automobile in such a low-speed mode, the torque (i.e., passing torque) that has passed through the toroidal-type continuously variable transmission 25 is applied to the output side disk 17a from the input shaft 1 by way of the carrier 27, the first transmission shaft 29, the sun gear 33, and the hollow rotary shaft 32. The torque is further applied from the output side disk 17a to the input side disks 2, 2 by way of the power rollers 20, 20. Specifically, the torque passing through the toroidal-type continuously variable transmission 25 during acceleration or constant-speed driving is circulated in the direction in which the input side disks 2, 2 experience the torque output from the power rollers 20, 20.
On the other hand, in a so-called high-speed mode in which the low-speed clutch 40 is disconnected and the high-speed clutch 41 is connected, the power of the input shaft 1 is transmitted to the output shaft 38 by way of the first and second transmission shafts 29, 31. The transmission ratio of the entire continuously variable transmission apparatus is changed by means of changing the transmission ratio of the toroidal-type continuously variable transmission 25. In this case, the higher the transmission ratio of the toroidal-type continuously variable transmission 25, the higher the transmission ratio of the entire continuously variable transmission apparatus.
During acceleration or constant-speed driving in such a high-speed mode, the torque having passed through the toroidal-type continuously variable transmission 25 is applied in the direction in which the input side disks 2, 2 apply torque to the power rollers 20, 20.
U.S. Pat. No. 6,251,039 describing the continuously variable transmission apparatus such as that mentioned above discloses only the principle of the speed-variable drive but fails to disclose a specific structure. On the other hand, when the continuously variable transmission apparatus is embodied, a contrivance must be applied to a structure of a coupling section between one input side disk 2 constituting the toroidal-type continuously variable transmission 25 and the carrier 27 constituting the planetary gear mechanism 26. Specifically, as shown in FIG. 9, in the case of a continuously variable transmission apparatus of a so-called geared neutral type, when the output shaft 38 is stopped or rotated at a very low speed while the input shaft 1 is being rotated, the torque passing through (circulating) the toroidal-type continuously variable transmission 25 becomes extremely large. Accordingly, the coupling section must possess sufficient strength to transmit such large torque.